Ultrasensitive sandwich-type prostate specific antigen immunosensor based on Ag overgrowth in Pd nano-octahedrons heterodimers decorated on amino functionalized multiwalled carbon nanotubes

A novel and ultrasensitive sandwich-type electrochemical immunosensor was designed for quantitative detection of prostate specific antigen (PSA). The Ag overgrowth in Pd nano-octahedrons, developed Pd-Ag heterodimers (Pd-Ag HDs), loaded on amino functionalized multiwalled carbon nanotubes (MWCNTs-NH 2 ) were employed as labels of secondary antibodies (Ab 2 ). The synergistic effect of Pd-Ag HDs exhibited high electrocatalytic activity towards the reduction of H 2 O 2 . MWCNTs-NH 2 with good dispersion , plentiful amino groups and large specific surface area , could load a large number of Pd-Ag HDs to enhance the sensitivity and amplify the signal of the immunosensor. Moreover, the electroplated gold nanoparticles (Au NPs) were employed for the immobilization of primary antibodies (Ab 1 ). Au NPs with excellent conductivity could enhance the electron transport between substrate material and electrode surface , and improve the sensitivity of immunosensor. Under optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.1   pg/mL–30   ng/mL towards PSA, and a low detection limit of 0.03   pg/mL (S/N   =   3). The proposed immunosensor exhibited good sensitivity, reproducibility and stability for the quantitative detection of PSA, which hold a great potential in clinical and diagnostic applications.